We know that Saturn has rings and with a moderately powerful home telescope, we can see them. But in 2009, a team of astronomers, using the Spitzer Space Telescope, discovered a huge new ring that had never been seen before. Despite the gigantic size of the new ring, it is made up of such a thin layer of dust and ice that it had never been noticed.

Let’s put things into some scale. Here are the numbers on the inner rings of Saturn:

The new ring has been called the “Phoebe Ring”, named after the moon of Saturn that marks the location of the giant ring. Let’s label it the “P” ring and add the new numbers for it:

Ring

Saturn radii

Kilometers

Miles

Earth diameters

P ring – 2009

205.748

12,400,000

7,700,000

972.092

It completely dwarfs the inner rings!

It’s also interesting to note that while all the inner rings of Saturn and most of it’s moons rotate/orbit in the same direction as the planet (prograde), both Phoebe and the new “P” ring rotate/orbit in the opposite direction (retrograde).

And now, the most recent data shows this ring is even larger than it was thought when it was discovered in 2009:

This diagram illustrates the extent of the largest ring around Saturn, discovered by NASA’s Spitzer Space Telescope. The ring is huge, and far from the gas planet and the rest of its majestic rings.

The bulk of the ring material starts about six million kilometers (3.7 million miles) away from the planet and extends outward roughly another 12 million kilometers (7.4 million miles). The diameter of the ring is equivalent to 300 Saturns lined up side to side. The ring is thick too — it’s about 20 times as thick as the diameter of the planet. In fact, the entire volume of the ring is big enough to hold one billion Earths!

First, let’s start with some background on the scale of Saturn’s known rings. (Click here to skip the background and go straight to the Spitzer results.) You can measure the extent of the rings in kilometers, but astronomers and Cassini mission people both seem to find “Saturn radii” to be a handier unit that helps them have a better intuitive feel for the scale of things. One Saturn radius, abbreviated as R-subscript-s but usually written just as Rs to make things easier, is 60,330 kilometers. Beginning at Saturn’s center, one radius gets you to Saturn’s cloud tops. The main ring system, the part that’s almost perfectly flat and aligned with Saturn’s equator, includes the D, C, B, A, and F rings and is just a bit more than twice Saturn’s diameter.

A small team of researchers with members affiliated with the University of Maryland, the University of Virginia and Caltech, has found that the outermost ring of Saturn is much bigger than had been previously thought. In their paper published in the journal Nature, the team describes how they studied the ring using an infrared telescope and what they believe caused its immense size to come about

Back in 2009, a team of researchers working with NASA’s infrared Spitzer Space Telescope discovered that there was an outer ring circling Saturn that had not been known to exist—made mostly of extremely tiny dark dust particles, the ring was difficult to see. They estimated at the time that the ring was likely over two hundred times the radius of its host planet. In this new effort, the researchers studied images taken from NASA’s WISE probe, which has also been taking infrared pictures. Those pictures, the team reports, suggest the ring is actually over 270 times the radius of Saturn, which mean it stretches from almost four million miles from the planet to just over ten million miles, making it approximately ten times the size of the E ring, until this new discovery, Saturn’s largest ring. Putting it into perspective, if Saturn were merely the size of a basketball, this new outer ring would extend nearly two thirds the length of a football field away from it.